Understanding Torque for Quarter-Turn Valves

Valve manufacturers publish torques for his or her products in order that actuation and mounting hardware may be correctly chosen. However, revealed torque values typically represent only the seating or unseating torque for a valve at its rated strain. While these are essential values for reference, published valve torques don’t account for actual installation and operating traits. In order to determine the precise operating torque for valves, it’s needed to understand the parameters of the piping systems into which they are put in. Factors similar to installation orientation, path of circulate and fluid velocity of the media all impression the precise working torque of valves.
Trunnion mounted ball valve operated by a single acting spring return actuator. Photo credit score: Val-Matic
The American Water Works Association (AWWA) publishes detailed data on calculating operating torques for quarter-turn valves. This data seems in AWWA Manual M49 Quarter-Turn Valves: Head Loss, Torque, and Cavitation Analysis. Originally printed in 2001 with torque calculations for butterfly valves, AWWA M49 is presently in its third edition. In addition to information on butterfly valves, the present version also consists of operating torque calculations for different quarter-turn valves including plug valves and ball valves. Overall, this handbook identifies 10 components of torque that may contribute to a quarter-turn valve’s operating torque.
Example torque calculation summary graph
AWWA QUARTER-TURN VALVE HISTORY
The first AWWA quarter-turn valve normal for 3-in. by way of 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and one hundred twenty five psi strain lessons. In 1966 the 50 and a hundred twenty five psi stress classes were increased to seventy five and 150 psi. เกจวัดแรงดันไฮดรอลิค was added in 2000. The 78-in. and bigger butterfly valve normal, C516, was first revealed in 2010 with 25, 50, seventy five and a hundred and fifty psi stress classes with the 250 psi class added in 2014. เกจวัดแรงดันน้ำไทวัสดุ -performance butterfly valve commonplace was published in 2018 and consists of 275 and 500 psi strain courses as properly as pushing the fluid circulate velocities above class B (16 toes per second) to class C (24 feet per second) and class D (35 feet per second).
The first AWWA quarter-turn ball valve standard, C507, for 6-in. through 48-in. ball valves in one hundred fifty, 250 and 300 psi stress lessons was printed in 1973. In 2011, size vary was elevated to 6-in. via 60-in. These valves have all the time been designed for 35 ft per second (fps) most fluid velocity. The velocity designation of “D” was added in 2018.
Although the Manufacturers Standardization Society (MSS) first issued a product normal for resilient-seated cast-iron eccentric plug valves in 1991, the primary a AWWA quarter-turn valve normal, C517, was not published till 2005. The 2005 size range was three in. through 72 in. with a one hundred seventy five
Example butterfly valve differential stress (top) and move price control windows (bottom)
strain class for 3-in. through 12-in. sizes and a hundred and fifty psi for the 14-in. via 72-in. The later editions (2009 and 2016) have not elevated the valve sizes or stress classes. The addition of the A velocity designation (8 fps) was added in the 2017 version. This valve is primarily used in wastewater service the place pressures and fluid velocities are maintained at lower values.
The want for a rotary cone valve was acknowledged in 2018 and the AWWA Rotary Cone Valves, 6 Inch Through 60 Inch (150 mm through 1,500 mm), C522, is under growth. This commonplace will encompass the same a hundred and fifty, 250 and 300 psi strain lessons and the same fluid velocity designation of “D” (maximum 35 ft per second) as the current C507 ball valve commonplace.
In basic, all the valve sizes, move rates and pressures have increased since the AWWA standard’s inception.
COMPONENTS OF OPERATING TORQUE
AWWA Manual M49 identifies 10 parts that affect working torque for quarter-turn valves. These elements fall into two common categories: (1) passive or friction-based elements, and (2) lively or dynamically generated parts. Because valve producers can not know the precise piping system parameters when publishing torque values, revealed torques are generally restricted to the 5 elements of passive or friction-based parts. These embody:
Passive torque elements:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The different 5 components are impacted by system parameters similar to valve orientation, media and move velocity. The components that make up energetic torque embrace:
Active torque elements:
Disc weight and middle of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these varied lively torque components, it’s possible for the actual working torque to exceed the valve manufacturer’s published torque values.
WHY IS M49 MORE IMPORTANT TODAY?
Although quarter-turn valves have been used within the waterworks trade for a century, they are being uncovered to higher service strain and circulate fee service situations. Since the quarter-turn valve’s closure member is at all times positioned within the flowing fluid, these higher service situations directly influence the valve. Operation of these valves require an actuator to rotate and/or hold the closure member throughout the valve’s body because it reacts to all of the fluid pressures and fluid circulate dynamic situations.
In addition to the increased service situations, the valve sizes are additionally growing. The dynamic situations of the flowing fluid have larger impact on the bigger valve sizes. Therefore, the fluid dynamic results become extra necessary than static differential strain and friction masses. Valves could be leak and hydrostatically shell examined during fabrication. However, the total fluid circulate situations cannot be replicated earlier than website installation.
Because of the trend for increased valve sizes and elevated working circumstances, it’s more and more necessary for the system designer, operator and proprietor of quarter-turn valves to raised understand the impression of system and fluid dynamics have on valve choice, building and use.
The AWWA Manual of Standard Practice M forty nine is dedicated to the understanding of quarter-turn valves together with working torque necessities, differential strain, move circumstances, throttling, cavitation and system installation variations that immediately influence the operation and profitable use of quarter-turn valves in waterworks systems.
AWWA MANUAL OF STANDARD PRACTICE M49 4TH EDITION DEVELOPMENTS
The fourth version of M49 is being developed to incorporate the modifications within the quarter-turn valve product standards and installed system interactions. A new chapter might be devoted to methods of control valve sizing for fluid flow, stress control and throttling in waterworks service. This methodology consists of explanations on the usage of stress, flow fee and cavitation graphical windows to supply the user an intensive picture of valve efficiency over a spread of anticipated system working circumstances.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his career as a consulting engineer in the waterworks trade in Chicago. He joined Val-Matic in 2011 and was appointed president of Val-Matic in May 2021, following the retirement of John Ballun. Dalton previously worked at Val-Matic as Director of Engineering. He has participated in requirements developing organizations, together with AWWA, MSS, ASSE and API. Dalton holds BS and MS levels in Civil and Environmental Engineering along with Professional Engineering Registration.
John Holstrom has been concerned in quarter-turn valve and actuator engineering and design for 50 years and has been an energetic member of each the American Society of Mechanical Engineers (ASME) and the American Water Works Association (AWWA) for greater than 50 years. He is the chairperson of the AWWA sub-committee on the Manual of Standard Practice, M49, “Quarter-Turn Valves: Head Loss, Torque and Cavitation Analysis.” He has additionally labored with the Electric Power Research Institute (EPRI) in the development of their quarter-turn valve performance prediction methods for the nuclear energy trade.
Share